Helij

2
He
Skupina
18
Perioda
1
Blok
s
Protons
Electrons
Neutrons
2
2
2
General Properties
Vrstno število
2
Atomska teža
4,002602
Mass Number
4
Kategorija
Žlahtni plini
Barva
Brezbarven
Radioactive
Ne
From the Greek word helios, the sun
Kristalna struktura
Ploskovno centrirana kubična
Zgodovina
French astronomer Jules Janssen obtained the first evidence of helium during the solar eclipse of 1868.

Norman Lockyer and Edward Frankland suggested the name helium for the new element.

In 1895, Sir William Ramsay discovered helium in the uranium mineral cleveite.

It was independently discovered in cleveite by Per Teodor Cleve and Abraham Langlet.
Electrons per shell
2
Razporeditev elektronov
1s2
He
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures
Physical Properties
Faza snovi
Plin
Gostota
0,0001785 g/cm3
Tališče
0,95 K | -272,2 °C | -457,96 °F
Vrelišče
4,22 K | -268,93 °C | -452,07 °F
Talilna toplota
0,02 kJ/mol
Izparilna toplota
0,083 kJ/mol
Toplotna kapaciteta
5,193 J/g·K
Abundance in Earth's crust
5,5×10-7%
Abundance in Universe
23%
Vial
Zasluge za slike: Images-of-elements
Vial of glowing ultrapure helium
CAS Number
7440-59-7
PubChem CID Number
23987
Atomic Properties
Atomski polmer
31 pm
Kovalentni polmer
28 pm
Elektronegativnost
-
Ionization Potential
24,5874 eV
Atomic Volume
27,2 cm3/mol
Toplotna prevodnost
0,00152 W/cm·K
Oksidacijska stanja
0
Applications
Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography.

Helium at low temperatures is used in cryogenics.

Helium is used for filling balloons and for pressurizing liquid fuel rockets.

Helium is used as a shielding gas in arc welding processes.
Helium is not known to be toxic
Isotopes
Stable Isotopes
3He, 4He
Unstable Isotopes
5He, 6He, 7He, 8He, 9He, 10He